Wednesday, June 8, 2011

The Persian Dastgāh System

An obsession of mine over the past several months has been the family of music traditions of the Middle East, most especially the Persian dastgāh system. A dastgāh is a collection of related "modes" and associated melodic rules. In theory, there are more than fifty such collections in existence, though twelve standard dastgāhs were codified in the 19th Century and are widely practiced today.

Each "mode" in a dastgāh consists of seven core pitches, to which further pitches are added to accommodate modulation or expression. These are not exactly modes in the Western sense, because the widths of certain intervals differ from one "mode" to another. As a result, a given instrument is limited only to certain sets of possible "modes" without being retuned (unless it uses a compromised tuning such as those detailed below).

A dastgāh also entails established practices regarding the role or function of each pitch in a "mode" over the course of musical development; these practices are known as sayr. Additionally, many short melodic fragments known as gushehs are incorporated into the larger context of each performance; how these gushehs are handled is part of the artistry of an individual performer. The full set of dastgāhs, with their associated sayr and gushehs, is called the radif.

Music historians consider the dastgāh system to have its roots in the court of Xosrov II, ruler of the Persian Empire from AD 590 to 628. He was patron to the musician Bārbod, who organized a musical system containing seven Royal Modes (Xosrovāni), thirty related modes (Lahn), and 360 melodies (Dastān). When the Persians were conquered in AD 642, Bārbod's system became the basis for the Arabic system of maqām (and thereby the Turkish makam); many of the original Persian names survive in the present-day maqāmat (the plural form).

The matured dastgāh system of modes and melodies grouped together into collections emerged by the end of the 19th Century, though there is little surviving evidence of the specific developments up to that time. Like the Arabic and Turkish systems, the dastgāh tradition has been passed down aurally through history by its practitioners, very few of whom left any written records. As such, tunings for the same dastgāh can vary from region to region, or even between cities or individuals.

Several attempts have been made to standardize a tuning system that could be used in which all dastgāhs could be represented with an acceptable degree of fidelity:

• In the 13th Century, Safiaddin Ormavi devised a scale with 17 tones per octave that ostensibly became the standard of Middle Eastern music theory for several centuries; however, it is not likely this system was adhered to in practice, given the nature of the instruments, the fact that most music used only about seven tones at a time, and especially the inherent variability of the aural tradition.

• Impressed with the advanced developments of European harmonic techniques and desiring to incorporate them into their own traditions, some prominent Middle Eastern musicians in the 19th and 20th centuries (notably Mikhail Mashaqa and Ali Naqi Vaziri) advocated the adoption of an equal temperament; however, because the semitone was too large to accommodate all traditional intervals, a further subdivision to a quarter-tone was proposed. The resulting 24-tone scale has found some favor for its relative practicality, as existing 12-tone instruments can be used (a basic technique involves splitting a composition between two pianos with one tuned a quarter-tone apart from the other), though many consider this tuning a poor compromise at best and culturally inappropriate at worst.

• In the 1940s, a physicist named Mehdi Barkesli conducted studies to measure the actual intervals used in practice by several Persian singers in various modes. Influenced by the writings of respected medieval scholars such as Ormavi, he presented a 22-tone scale as a means to unite all dastgāhs into a common tuning. However, this scale is built on a 7-tone scale from which the remaining tones are derived, but the basic scale itself is arbitrary, and the additional tones are calculated by means that have little relevance to actual practice.

Each of these systems makes the assumption of octave equivalence, though in reality the interval of a perfect octave may not even be present; pitches exist individually, not as members of a pitch class that repeats an octave higher or lower. Furthermore, as each pitch is an individual entity, it is inappropriate to consider one pitch a modified (raised or lowered) form of another, as is often done under influence from the Western tradition of sharps and flats.

In 1965, Hormoz Farhat presented his theory of flexible intervals in the dastgāh system. He identified five characteristic intervals from which the Persian modes may be constructed, and recognized the inherently approximate nature of these intervals in practice. These intervals range from about 90 cents (slightly smaller than the semitone of 12-tone equal temperament, though very close to the Pythagorean interval of 256:243 on which it is historically based) to about 270 cents (called a "plus-tone" by Farhat, it is significantly smaller than a minor third and perhaps best thought of as an augmented second). With this approach, there is no assumption of octave equivalence, and individual pitches serve distinct roles.

In addition to dastgāh itself, I have been studying the closely related Turkish makam, particularly the work of Karl Signell. He also identifies five characteristic intervals of makam, though two of the intervals are each about 20 cents different from their counterparts presented for dastgāh by Farhat. The makam intervals Signell offers are all multiples of a basic comma of about 23 cents (in his glossary, he identifies it as the Pythagorean comma, which has a value of 23.46 cents, though the numbers he provides for the intervals strongly suggest he actually uses the Holdrian comma of 22.64 cents, which indeed has been used by noted Turkish composers and theorists). He explains that the number of commas stacked to produce a given interval can vary; thus, those two intervals that differ between Farhat's dastgāh and Signell's makam could easily be adjusted with the addition or removal of a comma.

FARHAT

SIGNELL

90¢

90¢

135¢

114¢

160¢

180¢

204¢

204¢

270¢

271¢

There is still much for me to learn in this area, and I'm very excited to see where it leads. I'm curious to try using those five basic intervals, perhaps with appropriate adjustments to the number of stacked commas, to build some musically useful non-traditional modes, taking advantage of the precise tuning afforded by modern electronics. I also plan to study the rhythmic aspects of Middle Eastern music, which are based on cycles called uṣūl and more recently on the meter of a form of poetry known as ghazal, though that is definitely a subject for another day.